Doctorat en Physique
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Département de Physique
Université Hassiba Benbouali de Chlef,Faculté des sciences BP 151
Hay Salem, route nationale N° 19
02000 Chlef, Algérie
Tel: 027-72-70-17
Email: Bio_uhbc@univ-chlef.dz
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Item Single and double A light hypernuclei(Belabbas Mohamed / Margueron Jérôme, 2026-04) BOUTAMI KenzaItem Mathematical and Numerical Analysis of the Non Linear Schrödinger Equation(Chaachoua Sameut Houria / P.S vinayagam, 2026) TAIBI, ZEYNEBThis thesis presents a comprehensive analytical and numerical investigation of localized nonlinear wave structures governed by integrable Higher-Order Nonlinear Schrödinger (HNLS)-type equations. Motivated by recent advances in nonlinear wave physics and the increasing relevance of higher-order dispersive and nonlinear effects, this work demonstrates that the interplay between dispersion, nonlinearity, and higher-order terms constitutes a powerful framework for energy localization and control rather than a limitation. The study begins with a detailed overview of fundamental nonlinear wave phenomena, including solitons, breathers, and rogue waves, together with a rigorous analysis of modulation instability as the underlying mechanism for localized structure formation. Numerical tools, particularly the Split-Step Fourier Method (SSFM), are introduced and validated through the relative L 2 error norm and trajectory tracking based on the center-of-mass formalism. From an analytical perspective, the thesis employs the 3 × 3 Lax pair representation and the Darboux Transformation to construct exact solutions for integrable systems. These methods are applied to benchmark models such as the Hirota and Sasa–Satsuma equations, illustrating the iterative generation of higher-order solitonic and breather solutions and confirming the robustness of the analytical framework. The dynamics of the HNLS equation with constant coefficients are investigated in detail, revealing the role of spectral parameters in shaping wave morphology, including Akhmediev breathers, Kuznetsov–Ma solitons, and the Peregrine soliton as a limiting rational solution. The individual influence of higher-order physical parameters is isolated, highlighting the dominant role of third-order dispersion in inducing center-of-mass shifts and trajectory drift. Finally, the thesis extends the analysis to generalized HNLS equations with time-dependent coefficients, demonstrating that active modulation of dispersion and nonlinearity enables precise waveform engineering. Numerical simulations confirm the stability and physical relevance of the Darboux-derived solutions, with relative L 2 errors on the order of 10−4 , validating that the observed dynamics arise from intentional parametric control rather than numerical artifacts. Overall, this work provides a unified analytical–numerical framework for understanding and managing localized nonlinear wave phenomena, offering insights relevant to nextgeneration nonlinear physical systems in optics, hydrodynamics, and related fields.Item Ultra-cold gases in Low Dimensionality(BENAROUS MOHAMED / HOCINE AHMED, 2026) Medani, MohammedThis thesis investigates the thermodynamic properties of ideal Bose gases within the framework of the Dunkl formalism, a generalization of quantum mechanics based on the deformed Heisenberg algebra introduced through the Wigner-Dunkl differential-difference operator. Starting from the mathematical foundations of deformed algebras and revisiting the seminal contributions of Wigner, Yang, and Dunkl, we systematically extend the standard Bose-Einstein condensation theory to the Dunkl-deformed setting, covering both homogeneous and confined systems in arbitrary spatial dimension D. For ideal Bose gases confined by general power-law trapping potentials, we show that all thermodynamic quantities depend solely on a single universal parameter s that encoding the combined effects of dimensionality and trap geometry η. This reveals the existence of universality classes applicable to any power-law potential regardless of its specific form. Bose-Einstein condensation occurs exclusively for s > 1 , consistently with the Mermin-Wagner-Hohenberg theorem, and the BEC transition remains second order for all s ̸= 2, while s = 2 it exhibits a continuous transition of Berezinskii-Kosterlitz-Thouless type. The Dunkl deformation parameter ν tunes the thermodynamic behavior continuously, and thermodynamic consistency requires 0 < ν ≤ 2 , a constraint shown to hold for arbitrary regular potentials in any dimension. These results establish a unified description of Dunkl-deformed Bose gases and clarify the fundamental interplay between confinement geometry and algebraic deformation.Item Study of thermo-photovoltaic cells based on quantum nanostructures of III-V materials(RACHED Habib, 2025) TRAICHE, MOHAMMEDIn this work, we investigate the performance of a new generation of thermo-photovoltaic (TPV) cells engineered from hybrid quantum nanostructures based on III–V semiconductor materials. The main objective of our research is to exploit the synergistic integration of narrow band-gap antimonides with the unique optoelectronic properties of III–V alloys, thereby enabling ultrabroadband absorption extending from the visible to the far-infrared domain. This spectral versatility opens the pathway for significantly enhanced photoelectric conversion efficiency, surpassing the limits of conventional photovoltaic technologies. The novelty of this study lies in the nanotechnology-driven design of the active medium: by tailoring the dimensional confinement of carriers in 0D quantum dots, 1D quantum wires, and 2D quantum wells, it becomes possible to precisely control absorption, carrier transport, and thermal management. Such nanostructuration not only broadens the optical response but also enhances phonon scattering and thermal stability, key challenges in high-performance TPV systems. The proposed approach thus provides a multifunctional platform that unites photovoltaic and thermoelectric effects within a single hybrid device, this research demonstrates a pathway toward highly efficient, spectrally versatile, and thermally robust energy conversion devices, positioning hybrid nanostructured TPVs as a disruptive technology in the future of renewable and sustainable energy.Item Etude ab-initio des propriétés structurales, magnéto-électroniques des alliages d’Heusler quaternaires(RACHED Habib, 2025-06-30) NOURINE, RACHIDAIn this work, the structural, electronic and magnetic properties of some quaternary Heusler alloys (QH) based on RhCo were calculated using an ab-initio method. These compounds can be generated from doping of the ternary Heusler compounds; in this case, we begin our study by following the variation of structural, electronic and magnetic properties of Cobalt-doped of Rh2MnSn. The Co-substitution at Rh sites of Rh2-xCoxMnSn (x = 0 to 2) transforms it to half metallic material from the concentrations more than x=0,75. The magnetic properties reveal that the Co-doping increases the total magnetic moment; it is equal to 4.68 μB for Rh2MnSn to reach 5 μB in the range of half-metallic compounds founds. This integer value is obeying the Slater Pauling behavior with a 100% spin polarization. The exchange interaction parameters ( jij) and the Curie temperatures (Tc) of RhCoMnZ (Z = Al, Si, Ga, Ge, Sn, Sb) are also estimated, using the LMTO method implemented in the Questaal package. The Tc is calculated with mean field approximation (MFA), it is higher than ambient temperature for all compounds studied making them promising candidates for spintronic devices.Item Etude ab-initio des propriétés structurales, magnéto-électroniques des alliages d’Heusler quaternaires(RACHED Habib, 2025-06-30) NOURINE, RACHIDADans ce travail, les propriétés structurelles, électroniques et magnétiques de certains alliages de heusler quaternaire (QH) basées sur RhCo ont été calculées à l'aide d'une méthode ab-initio. Ces composés peuvent être générés par le dopage des composés heusler ternaires; dans ce cas, nous commençons notre étude en suivant la variation des propriétés structurelles, électroniques et magnétiques des Rh2MnSn dopés au cobalt. La substitution du Co aux sites Rh de Rh2-xCoxMnSn (x = 0 à 2) le transforme en un matériau demi-métallique pour les concentrations supérieures à x = 0,75. Les propriétés magnétiques révèlent que le Co augmente le moment magnétique total; il est égal à 4,68 μB pour que Rh2MnSn et atteigne 5 μB pour le reste des composés demi-métalliques trouvés. Cette valeur entière obéissait au comportement SlaterPauling avec une polarisation de spin de 100%. Les paramètres d'interaction d'échange (jij) et les températures Curie (TC) de RhCoMnZ (Z = Al, Si, Ga, Ge, Sn, Sb) sont estimés, en utilisant la méthode LMTO implémentée dans le package Questaal. La TC est calculé avec l’approximation du champ moyen (MFA), il est plus élevé que la température ambiante pour tous les composés étudiés, ce qui en fait des candidats prometteurs pour les dispositifs spintroniques.Item DYNAMICS OF BINARY MIXTURES AT ULTRA COLD TEMPERATURES: EFFECTS OF INTERSPECIES CORRELATIONS(Hocine Ahmed / Benarous Mohamed, 2025) MEHEDI, AtikaThis do ctoral work intends to take account of dynamical correlations in binary mixtures of Bose-Ein stein condensates (BEC), comp osed of two distinct sp ecies. In a p rel imi nary analysis, we consider a purely one-dimensional mixture, where the anomalous (or off-diagonal) correlations are finite and do not requ ire any renormalization. Their b ehavior, examined within a variational framework usin g a gau ssian density op erator, corrob orate a preceding result assessing that the anomalous and non cond ensate densities are of the same order and, therefore, any approach con sidering only non condensate densities can only b e viabl e at very low temp erature (or zero temp erature) or near the transition. This was demonstrated numerically by solving a set of self-consistent equations. Furthermore, in a binary mixture, a set of unprecedented correlations app ears . Indeed, b eside the intras p ecies correlations, we shed light on intersp ecies correlations, which depict the entanglement b etween the sp ecies In the vaste literature, we noticed that these effects are generally omitted owing to the fact that, in many exp eriments, the entanglement b etween different sp ecies is considered as marginal. We show however in this work, that it n eed s not b e the case in a general context. These effects are however quite tiny and cannot b e observed in situations where the mean field is dominant. Hence, we considered situations where the mean -field is almost zero. This fortunately happ ens for a binary system when the intersp ecies interactions are attractive an d almost neutralize the interasp ecies ones. This lead s to self-b oun d states named droplets which were indeed dis covered exp eri mentally. We therefore fo cused on droplets in quasi-one dimensional geometries and exhibited the dominant role of intersp ecies fluctuations. We showed that the droplet states are more stable and therefore more easily ob servable when one includes intersp ecies correlations. We also show that these effects add up to the LHY contributions extending th e b eyond mean-field theory in the Bogoliub ov framework. This work was p erformed in a consistent and metho dic way which led to original results published in journal of low temp erature physicsItem Bose Gases In Deformed Algebra(Hocine Ahmed / Hamil Bilel, 2025-04-28) MERABTINE, FATEHThis thesis explores the impact of the Dunkl formalism, a mathematical framework incorp orating a reflection term controlled by the Wigner parameter θ , on quantum statistical mechanics, particularly Bose-Einstein condensation (BEC) and related phenomena. It examines how Dunkl mo dification alters the prop erties of an ideal Bose gas, including statistical and thermo dynamic b ehaviors, and mo difies blackb o dy radiation, such as the Stefan-Boltzmann law. The research extends to BEC in harmonic and p ower-law traps, showing how θ influences critical temp eratures, condensate fractions, and thermo dynamic prop erties like sp ecific heat capacity. Key findings highlight mo dified thermo dynamic relations, invariant quantities under Dunkl transformation, and unique scaling b ehaviors, demonstrating the formalism’s p otential for advancing understanding of quantum systems and their applications. frenchItem Résolution des problèmes en physique du système des potentiels diatomiques via les intégrales de chemin.(H. Boukabcha / M. Belabbas, 2024-10-24) AID, SALAH EDDINEThis thesis uses Feynman’s path integrals formalism to exp lore quantum systems from b oth relativistic and non-relativistic p ersp ectives. We have provided a brief overview of the p ath integral approach an d the Duru-Kleinert space-time transformation. Three problems have b een examined for the non-relativistic regime: the trigonometric Pöschl-Teller, the mo dified Pöschl-Teller and the Generalized Inverse Quadratic Yu kawa (GIQY) Potentials. Our approach to the fi rst two problems involves expanding the available s-states solutions using the Greene-Aldrich approximation scheme to comp ensate for the centrifu gal term. However, in addition to approximating the 1/r and 1/r2 terms, the Generalized Inverse Quadratic Yukawa Potential treatment relied on an appropriate space-time transformation that allowed the propagator to be reduced to that of a modified Pöschl-Teller problem. We have compared the results to some previous approaches and it was satisfactory. For the relativistic regime, two problems have been considered: we have investigated the problem of a spinless particle subjected to Generalized Inverse Quadratic Yukawa potential. Path integral representation and its corresponding Green’s function has been derived with the help of the previous space-time transformation. Particular cases were also considered, which made it possible to make comparison with other results obtained differently. As a second relativistic problem we have dealt with a spin-1/2 particle in vector and scalar potentials of GIQY type. Both spin and pseudospin symmetries were taken into account. From the four coupled partial differential equations included in Dirac equation, two Schrödinger’s like equations has been derived . For every equation, a Green’s function has been evaluated. Thanks to a space-time transformation, we have been able to integrate the Green’s function and deduce the discrete spectrum energy levels and the upper and lower components of corresponding wave functions. numerical results and special cases were also presented in the last of this woItem Contribution à la modélisation de la détection biologique à base des nanomatériaux pérovskites Soutenue le(Oussama ZEGGAI / Mousaab BELARBI, 2025-01-20) BOUHENNA, AbdessalemCette thèse se concentre sur la modélisation et la simulation de biosenseurs innovants basés sur des matériaux de type pérovskite, en particulier le titanate de strontium (SrTiO3), pour la détection du cholestérol et des biomarqueurs du cancer. Les maladies cardiovasculaires et le cancer sont parmi les principales causes de mortalité dans le monde, et la détection précoce de ces maladies est essentielle pour améliorer les résultats cliniques. Cependant, les technologies de détection actuelles présentent encore des limites en termes de sensibilité, de spécificité et de coût. Les travaux de cette thèse visent à surmonter ces défis en développant des capteurs plus performants en intégrant des métasurfaces de graphène et d'or, ainsi que des matériaux pérovskites. Grâce à l'utilisation des outils de simulation avancés, notamment MATLAB et COMSOL, les performances des capteurs ont été optimisées en termes de sensibilité et de rapidité de réponse. Deux applications principales ont été étudiées : un biosenseur à effet de champ (BioFET) pour la détection du cholestérol et un capteur à résonance plasmonique de surface (SPR) pour la détection précoce du cancer. Les résultats obtenus démontrent que ces biosenseurs offrent une sensibilité et une spécificité accrues, ce qui ouvre la voie à des avancées significatives dans le diagnostic médical.Item Quantum droplets in random potentials(Abdelaali Boudjemaa, 2024) ABBAS, KarimaOne of the important achievements in the eld of ultracold atoms is the recent prediction and observation of ultradilute quantum liquid droplets, a new quantum state of matter. Quantum droplet originates due to the subtle balance between the attractive mean- eld force and the repulsive force provided by the Lee-Huang-Yang quantum uctuations. This thesis aims rst to study large bulk properties of self-bound quantum droplets of Bose mixtures in weak disorder potentials, and second introduces - nite size e ects within a generalized disorder-dependent Gross-Pitaevskii equation. Our investigation encompassed the examination of both uncorrelated and correlated disorders in three dimensions at zero and nite temperatures. We look in particular at how the intriguing interplay of the disorder, interspecies interaction and the Lee-Huang-Yang quantum uctuations a ect the formation and the stability of such a novel state of matter. New useful analytic expressions for the equation of state, equilibrium density, glassy fraction, depletion, and the anomalous density of the droplet are obtained in terms of the disorder parameters using the Bogoliubov-Huang-Meng theory. Our results reveal the signi cant role played by the strength and correlations of disorder in the stability and in self-evaporation phenomenon of the droplet state. At nite temperature, we analyze the free energy and the critical temperature above which the droplet evaporates. It is found that the competition between the thermal uctuations and disorder may strongly destabilize the droplet and completely destroy it above a certain critical temperature. We discuss the validity conditions of the present Bogoliubov theory. Furthermore, the structure and dynamics of the nite size quantum droplet in a three-dimensional random potential are explored by numerically solving the corresponding disorderdependent Gross-Pitaevskii equation. We also investigate the lowest-lying excitations of self-bound droplets employing a variational method. Our predictions point out that the peculiar interplay of the disorder and the repulsive Lee-Huang-Yang corrections leads to deform the atomic density in the at-top plateau region and to modify the collective modes of the self-bound droplet. Finally, our study is extended to one-dimensional geometry. We describe the bulk properties of disordered droplets using the aforementioned Bogoliubov method. We then conduct a numerical study in the purpose of revealing the impacts of weak random external potentials in two physically di erent regimes are identi ed, namely: small droplets of an approximately Gaussian shape and large droplets with a broad at-top plateau.Item Plasma Effect on Adsorbed Biomolecules(Abderrezak BERBRI / Ahmed BOUHEKKA, 2024-06-20) TADJINE, MoustafaIl est bien connu que l’étude des interactions des protéines avec les surfaces solides reste un défi de taille pour les scientifiques, en raison des paramètres qui contrôlent ce type d’adsorption. Les deux structures (protéine et surface) sont très compliquées, à bien identifier surtout lorsqu'elles entrent en contact. L'objectif de la présente recherche de thèse est d'étudier l'adsorption de la protéine d'albumine sérique bovine avec la surface du dioxyde de titane (TiO2) en modélisant, et en utilisant la spectroscopie de réflexion totale atténuée in situ. Un modèle cinétique étendu à deux états a été proposé et résolu analytiquement puis appliqué au cas de la protéine BSA expansée à la surface de l'anatase TiO2 à une valeur de pH de 1.7. où la constante du taux d'adsorption a été évaluée et en utilisant le modèle, nous avons pu déterminer la couverture de surface des états natifs et de déploiement des protéines. Une autre chose importante était l'étude de l'effet d'espace disponible libre pendant le processus de déploiement, et sa comparaison avec le modèle étendu où il était ignoré. Les résultats de cette recherche ont clairement démontré la nécessité d'une modélisation pour compléter la faiblesse expérimentale, et ont également illustré la différence entre les deux modèles avec et sans prise en compte de l'espace libre.Item Propagation des ondes électroniques dans les structures quantiques mésoscopiques à défauts sélectifs(Hafid KHALFOUN / Habib RACHED, 2024-05-14) KHEMISSI, AichaNous étudions les propriétés du transport électronique quantique dans des nanotubes de carbone (CNT) « armchair » contenants des atomes de bore B et d’azote N - en substitution - selon des arrangements réguliers en lignes de nitrures de bore BN. Pour ces structures, l’hybridation entre les orbitales atomiques C, et celles des atomes invitées B et N au sein de la structure tubulaire hôte, permettra la conception de nouveaux nanotubes BNC dits hybrides dont les propriétés physiques dépendront intiment des arrangements sélectifs de ces atomes à l’échelle atomique. Suivant l’axe du nanotube, la disposition géométrique des lignes BN est conforme aux géométries verticales et horizontales respectivement. Dans la direction circulaire, chaque géométrie est associée à une orientation parallèle et à une orientation antiparallèle, selon des dispositions identiques ou opposées de l’orientation spatiale de la paire BN le long du contour du nanotube. À ce sujet, nous examinons les propriétés du transport électronique de ces structures en étudiant les propriétés des structures de bandes d’énergie, du coefficient de transmission et des caractéristiques courant-tension (I-V), associées à ces structures, dans un processus de transport électronique à deux terminaux. Les calculs numériques ont été effectués sur la base du modèle mathématique de liaisons fortes associé à la théorie de la fonctionnelle de la densité, tel que implémenté dans le code de calcul DFTB+. En conclusion, l’orientation antiparallèle associée à des motifs BN sélectifs peut constituer un paramètre supplémentaire pouvant influencer significativement la propagation des ondes électroniques dans ces structures quantiques.Item Study of Molecules Adsorption onto Solid Surface(Ahmed BOUHEKKA / Abderrezak BERBRI, 2024-01-08) BOUZIDI, FatimaThe adsorption of water on rutile TiO2 (110) surface controls many chemical processes encountered in nature and industry. The key features of liquid-solid interfaces are the high mobility and often reactivity of the H2O molecules and the structural control provided by the solid species. There are several theoretical and experimental techniques of interest to elucidate the dynamics of water on surfaces. However, in this dissertation, we apply mathematical modelling methods to study these interactions: First, we investigated the behaviour of H2O molecules attached on the surface in case of stopping the incoming H2O flux before equilibrium, and we show how H2O behave under various temperature values and the initial coverage of H2O affected. Another point was to study the impact of oxygen vacancies and the amount of H2O flux in the dynamics of water on the rutile (110) surface, in the case of steady state, to control and enhance the production of OH. Our results clearly indicate that temperature, oxygen vacancies, the coverage of H2O adsorbed on surface and H2O flux have a marked effect on the dynamics of water, and it must be taken into account and controlled to achieve the desired applications. Besides, we are comparing the simple H2O molecules behaviour and complex adsorption of bio-molecules like bovine serum albumin (BSA) proteins on TiO2 surface, where the results demonstrated that the sticking of proteins on surface is accompanied by the expulsion of the adsorbed water and this overbalance to the hydrophobic core inside of the proteins particles which can affect its structure. Controlling the production of OH is very important in technology applications such as self-cleaning, especially in the purification and decomposition of water besides the splitting of water as well as in biotechnology.Item Diffusion multiple des ondes de matière à basse température dans un champ de speckle en dehors d'un piège harmonique(Afifa YEDJOUR / Abdelaali BOUDJEMAA, 2023-11-21) BENMAHDJOUB, HananeL’objectif principal des travaux de recherche de cette thèse de doctorat est d’étudier les défis real dans le transport quantique des atomes froids. Cette étude cherche à comprendre le processus de la propagation des atomes froids dans un champ de speckle tridimensionnels. Dans ce travail, trois études sont abordées. La première concerne l’étude du comportement de l’onde de matière dans les cas de diffusion simple et multiple. La deuxième s’intéresse à comprendre l’effet des grandeurs quantiques sur la propagation des ondes de matière dans un système désordonné tridimensionnels. La troisième se focalise autour de l’énergie critique, du nombre critique de l’onde de matière, de l’intensité critique du désordre pendant la transition des ondes de matière dans le milieu désordonné.Item Quantum droplets in Bose-Bose mixtures(Abdelaali BOUDJEMAA, 2023) GUEBLI, NADIAMost recent sensational breakthrough in the eld of ultracold atomic quantum gases is the creation of self-bound droplet state. This exotic phase of matter which can be formed in dipolar condensates and binary Bose mixtures, results from the competition between an attractive mean- eld energy and the repulsive Lee-Huang-Yang correction. This thesis looks to answer the question of e ects of higher-order quantum and thermal uctuations on the stabilization of self-bound droplets in Bose-Bose mixtures. Within the Hartree-Fock-Bogoliubov theory we calculate the ground-state energy, the droplet equilibrium density, the depletion and anomalous density of the droplet as well as the critical temperature as a function of the relevant parameters. Our ndings for the ground-state energy are compared with recent available analytical predictions and di usion Monte Carlo simulations and excellent agreement is found. We compute the density pro les and breathing modes of the droplet of this novel state of matter by numerically solving the underlying generalized nitetemperature Gross-Pitaevskii equation. This latter is derived selfconsistently from our theory using the local density approximation. We study also in this thesis the bulk and surface properties of ultradilute self-bound quantum droplets in a heteronuclear Bose-Bose mixture. Within the realm of the Hartree-Fock-Bogoliubov theory, we calculate beyond the Lee-Huang-Yang corrections to the ground-state energy, the droplet equilibrium density, the surface tension, and the critical number of particles. Our predictions coincide perfectly with recent di usion Monte Carlo simulation and density functional theory method.Item L’effet du dopage aux Chrome et Fer sur la structure électronique et les propriétés magnétiques et mécaniques des composés chalcogénures(Habib RACHED, 2023-07-02) MANCER, HemzaLe premier objectif de cette thèse est d’étudie l’effet des différentes approximations des fonctionnelles d’échanges et corrélations tels que la GGA-PBEsol, GGA+U, l’approche de Tran-Blaha du potentiel modifie de Becke-Johnson combiné avec la GGA+U (mBJ-GGA-PBEsol+U) sur les structures électroniques des composés chalcogénures Ag2O and Au2S. Le second objectif est de faire une enquête pour la première fois sur les composés précédents dopés par le Fe et Cr dans le but de prédire de nouveaux matériaux semi-conducteurs magnétiques dilués DMS. Tous nos calculs ont été faits par les méthodes de premier principes dans la base de la théorie de la DFT. Les résultats des propriétés structurales, élastiques et électroniques pour les composés binaires non dopés ont été obtenus et comparés avec les données existantes. Les structures électroniques ont révélés que les Ag2O and Au2S sont des semi-conducteurs à gap direct avec un gap d’énergies égal à 1.22 et 2.27 eV, respectivement. Ces valeurs sont en bonne accords pour la première fois avec celles obtenues expérimentalement. La stabilité, les propriétés magnéto-électroniques et élastiques des composés Ag2Cr2O2, Ag2Fe2O2, Au2Cr2O2, et Au2Fe2O2 ont été calculées et discutés en détails. Les résultats ont montrés que les composés Au2Cr2O2 et Au2Fe2O2 sont des matériaux ferromagnétiques demi-métalliques (HMF), tandis que les composés Ag2Cr2O2 et Ag2Fe2O2 sont des matériaux ferromagnétiques presque demi-métalliques (N-HMF).Item Calculs DFT des stabilités structurales, propriétés mécaniques, électroniques et optiques pour les alliages quaternaires Cu2Zn1−xCdxSnS4(Habib RACHED, 2023) TAGREROUT, ABDALLAHItem Binary mixtures with a time-dependent variational approach: new families of breathers in two-component condensates(Houria CHAACHOUA SAMEUT / Mohamed BENAROUS, 2022) BELKROUKRA, HalimaOur work is organized as follows. In chapter 1, we give a short historic and background about the nonlinear Schr odinger equation (NLSE) and its solitonic solutions. In chapter 2, we present the Balian-V en eroni time dependent variational principle, which is the main tool to derive the Gross-Pitaevskii equation (GPE) and its generalizations in a mean eld framework. Since these equations are highly nonlinear, they require special analytic tools. We present the general formalism of the Darboux transformation method and the Lax pair method. For readers who are not familiar with these methods, we present a simple example. In chapter 3, we focus on two component condensates where we nd solitonic solutions of the coupled Gross-Pitaevskii equations (CGPE). By transforming our model to a Manakov system via similarity transformation and employing Darboux transformation with zero seed, we observe that the introduction of an external trap leads to sudden shoots up in the atomic density indicating onset of dynamical instability. We pursue our analysis in chapter 4 by nding another type of solitons, namely the Peregrine solitons. The Darboux transformation is used in two cases. The symmetric case with the same seed solutions and the nonsymmetric case. One also observes the onset of dynamical instability as the frequency of the harmonic trap is varied. By a speci c choice of the spectral parameters, we show that these solitons may be stabilized. In chapter 5, we generalize our approach by letting free the spectral parameters. We nd general families of solitonic solutions parametrized by the spectral parameters. We derive not only the Peregrine solitons found previously, but also the standard families of Ma and Akhmediev breathers as well as new general breathers and rogue waves. In all these cases, we show that, by modulating the trap frequency, we are be able to stabilize the solitons against dynamical instability. In the last part of our work, we gather some conclusions and perspectives. 1Item Étude des propriétés de transports magnéto-électronique et thermoélectrique dans les composés full-Heusler à base des métaux alcalins(Hafid KHALFOUN / Habib RACHED, 2022-06-21) HADJI, TariqThis work intends to study from the first principles the structural stability, electronic, magnetic and thermoelectric properties of the new hypothetical full-Heusler compounds Mn2LiZ (Si, Ge, Sn, Al, Ga and In). We use the density functional theory implemented by the linearized augmented plane wave method to perform structural optimization and electronic structure calculations. As a main result, from the analysis of the total energies of different systems, we find that the compounds with Z is Si, Ge, Al and Ga are structurally, mechanically and thermodynamically more stable in the inverse Heusler structure (XA structure). The electronic structure investigation shows that Mn2LiSi, Mn2LiGe and Mn2LiSn are half-metallic ferrimagnetic with wide energy gaps and smaller total magnetic moments. We obtain a spin gapless semiconductor and nearly spin semimetallic properties with zero total spin moments in the Mn2LiAl and Mn2LiGa, respectively. The exchange interactions are determined within the Korringa-Kohn-Rostoker Green’s function framework. We show that the calculated inter-sublattice exchange interaction presents a dominant contribution to the exchange. Having determined the exchange interactions, we can deduce the Curie temperature in the mean-field approximation. Due to the large values of the inter-sublattice exchange reactions, we find that the Curie temperature is much higher than room temperature for all compounds, a prerequisite in spintronics. In the present study, we also calculated and discussed the electronic transport properties based on the semi-classical Boltzmann transport theory.